gh-100795: avoid unexpected freeaddrinfo after failed getaddrinfo (#101220)

Co-authored-by: Oleg Iarygin <[email protected]>

Author: sebres

Misc/NEWS.d/next/Library/2023-01-21-16-50-22.gh-issue-100795.NPMZf7.rst

@@ -0,0 +1,2 @@
+Avoid unexpected ``freeaddrinfo`` when :meth:`socket.socket.getaddrinfo`
+fails. Patch by Sergey G. Brester.

Modules/socketmodule.c

@@ -6719,6 +6719,7 @@ socket_getaddrinfo(PyObject *self, PyObject *args, PyObject* kwargs)
     error = getaddrinfo(hptr, pptr, &hints, &res0);
     Py_END_ALLOW_THREADS
     if (error) {
+        res0 = NULL;  /* avoid unexpected free if res0 becomes not NULL */
         set_gaierror(error);
         goto err;
     }
@@ -6815,6 +6816,7 @@ socket_getnameinfo(PyObject *self, PyObject *args)
     error = getaddrinfo(hostp, pbuf, &hints, &res);
     Py_END_ALLOW_THREADS
     if (error) {
+        res = NULL;  /* avoid unexpected free if res becomes not NULL */
         set_gaierror(error);
         goto fail;
     }